https://publications.parliament.uk/pa/cm201719/cmselect/cmcumeds/365/36503.htm
https://ec.europa.eu/commission/sites/beta-political/files/aviation.pdf
http://ukandeu.ac.uk/wp-content/uploads/2018/10/The-mechanics-of-a-further-referendum-on-Brexit-Constitution-Unit-Report-1.pdf
https://www.gov.uk/government/news/pms-european-council-press-statement-20-october-2017